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Experiment to investigate what effects the rate of respiration in yeast

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SC1 Experiment to investigate what effects the rate of respiration in yeast Aim To investigate the effect of temperature on the rate of respiration in yeast Glucose + Oxygen Carbon Dioxide + Energy + Water Introduction Respiration is catalysed by enzymes. Enzymes are proteins, the structure of which is affected by temperature. Most enzymes optimum temperature is 40 �C. All matter is made of particles, which move around. When heat is present the particles move around faster, colliding into each other, so they respire more. The hotter the water, the more they move around and vice versa. Prediction I predict that the highest rate of respiration will be at 40 �C. Above 40 �C, the rate of respiration will decline; this is because enzymes start to break down. This is called denaturing. I also predict that the yeast will not respire at a temperature of below 15 �C because the particles are not moving around enough. Apparatus Possible Variables * Temperature * Volume of Water * Concentration of Glucose solution * Mass of Yeast * Volume of Glucose solution Variable to be ...read more.


So I decided to stop recording results at 50 �C. Stopping the experiment at this point will prove that the enzymes break down after 40�C. I found that it was difficult to keep the water at a set temperature because it kept cooling down, so I put a plastic beaker outside the glass one, filling them both with the hot water. This method makes a double jacket, therefore keeping the water at a set temperature. The diagram below demonstrates the improved apparatus. Improved Apparatus Method * Set up apparatus as shown * Fill the boiling tube beaker up with 250 ml of water that is over 50 �C * Fill the CO� bowl up with 400 ml of water that is over 50 �C * Wait 10 minutes for the water to cool down to 50 �C * Measure out 3g of yeast and put it in the boiling tube * Measure out 15cm� of glucose solution and pour it on top of the yeast * Place the rubber tube up the boiling tube * Place the tube in the beaker and the ...read more.


I can see from the graph that the amount of CO� at 15 �C is only 1.1 cm�. See graph However, at 35 �C it has rapidly increased to 10.5 cm�. See graph And then at 50 �C the rate of respiration falls to 7.7 cm� again. See graph This proves that my prediction was accurate. Evaluation Overall I think the experiment went fairly well. The main points of error were in the reading of the amount of CO� collected as this was very difficult to judge and inaccuracies in timing. On the second set of results for 30 �C the result goes lower even though it should have been ascending like the rest of the results. This was because the stop watch was pressed at the wrong time. The double jacket worked well for maintaining the heat however time was still wasted waiting for the water to get down to its correct temperatures. As I said before reading the CO� collection tube was difficult, as was reading the thermometer ...read more.

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